1. Introduction

Neuropathic pain (NP) is a sensory abnormal disorder caused by neurological somatosensory lesions or nerve damage, characterized clinically by burning, radiating, and recurrent spontaneous pain.[1,2] The pathomechanism is closely related to nerve injury, peripheral or central sensitization injury.[3,4] With a prevalence of about 6.9%~10% in the general population, NP has become one of the major contributors to the global burden of disease.[5] The International Association for the Study of Pain classifies NP into 2 types: central and peripheral.[6] Central NP includes spinal cord injury, brain injury, fibromyalgia, and central post-stroke pain. Peripheral NP includes postherpetic neuralgia (PHN), primary trigeminal neuralgia, radiculopathy, and diabetic peripheral neuropathy (DPN). Several first-line drugs are currently used for the treatment of NP, including tricyclic antidepressants, calcium channel anticonvulsants, etc.[7] However, the clinical efficacy is unsatisfactory for most patients.[8] While opioids can be effective in relieving pain, the side effects associated with long-term use are still a huge challenge. Therefore, it is necessary to explore more about the novel potential treatment options for NP. It is believed that traditional medicine and new physical therapy have become promising and hopeful therapeutic strategies for NP.[9] Among them, complementary and alternative therapy (CAT) has received the attention of many researchers in recent years.

CAT is a method of treating illness that includes modalities such as herbal medicine, electroacupuncture (EA), acupuncture, cupping, yoga and meditation as a complementary or alternative to mainstream medicine.[10] CAT has been employed extensively recently to treat NP-related illnesses, including PHN,[11] fibromyalgia,[12] lumbar disc herniation,[13] peripherally induced NP,[14] etc. At the same time, although the number of studies is climbing year by year, there is a lack of quantitative analyses of research patterns, trends, and research hotspots regarding CAT for the treatment of NP.

Bibliometrics is a scientific method of using mathematics and statistics to measure and analyze a large amount of literature information collected.[15,16] The key information in the literature is integrated and clustered through network relationship diagrams, so as to reveal the characteristics of research in the subject area, the development lineage, the focus on hot spots and the direction of future development.[17,18]

In this study, bibliometric platform, VOSviewer and CiteSpace software were used to analyze the publications in the field of CAT for the treatment of NP from 2002 to 2022. The research characteristics, process and research hotspots in the field were explored from the aspects of countries, institutions, authors, keywords and references. This study can serve as a reference for researchers’ subsequent studies in this area.

2. Methods and strategies 2.1. Data collection and retrieval strategies

Publications included in this study were searched in the Web of Science Core Collection database (WoSCC) - Science Citation Index Expanded (SCI-Expanded) Editions on August 10, 2023. To ensure the comprehensiveness and reliability of the search, we determined the search strategy after repeated attempts. The search formula is TS = (“complementary/alternative medicine*” OR “transcutaneous electrical stimulation” OR “herbal medicine” OR “electroacupuncture” OR “acupuncture” OR “acupressure” OR “acupoint thread-embedding” OR “acupotomology” OR “cupping” OR “tuina” OR “massage” OR “scraping” OR “moxibustion” OR “Qigong” OR “Tai Chi” OR “hypnotherapy” OR “yoga” OR “meditation”) AND TS =(“neuralgia” OR “neuropathic pain” OR “neurodynia” OR “atypical neuralgia” OR “iliohypogastric nerve neuralgia” OR “paroxysmal nerve pain” OR “perineal neuralgia” OR “stump neuralgia” OR “supraorbital neuralgia” OR “nerve pain” OR “ilioinguinal Neuralgia” OR “nerve ligation” OR “nerve cut” OR “chronic constriction injury” OR “diabetic neuropathy” OR “nerve constriction” OR “sciatica” OR “peripheral neuropathy” OR “trigeminal neuralgia”) AND DOP = (2002-01-01/2022-12-31) AND LA = (English). The type of publication was selected as “article” and “review” and excluded “book chapters.” In the end, 1095 publications were retrieved. Figure 1 displays the flow chart of the article search and selection.

Figure 1.:

Flowchart of the literature search.

2.2. Data filtering and export

By reading titles, abstracts, and keywords, we filtered out irrelevant articles, resulting in a total of 898 publications. We exported 898 publications after screening as plain text file with “full record and cited references” for storage and named “download-XXX.” Ultimately, we imported these publications into CiteSpace for de-duplication, obtaining 898 documents for the bibliometric study.

2.3. Data analysis

Microsoft Excel 2021 was used to summarize the number of articles and citation frequency and to draw line graphs.

The bibliometric platform (https://bibliometric.com/) was used to statistically analyze the change of publication volume from 2002 to 2022 for each country.

VOSviewer is a scientific knowledge mapping software that can visually analyze the co-occurrence and cooperative relationship of research objects through “literature knowledge units.”[19,20] In our study, collaborations and co-occurrence between countries/regions, institutions, authors, and co-cited authors were analyzed by VOSviewer (version 1.6.19). Similarly, the maps of journals co-citation and references co-citation, keyword density were also made by VOSviewer.

CiteSpace is an information visualization software that can analyze and present the structure, patterns and distribution of knowledge.[21] In this paper, CiteSpace (version 6.1.R6) were used to make a dual-map overlay of journals, and the map of co-occurrence and timeline of keywords. Clustering and burst analysis of keywords and references were also performed using CiteSpace.

3. Results 3.1. Publishing and citation

After removing self-citation, a total of 898 publications, including 662 articles and 236 reviews, were cited 15,856 times (H-index = 60). The quantity of publications and the frequency of citations can show how a field is evolving over time. Figure 2 illustrates how the overall volume of publications and citations exhibits an upward tendency over time. A 96.8% average annual growth rate in the number of publications from 3 in 2002 to 124 in 2022 shows that the field of research has expanded significantly during the past 20 years. While there were fluctuations from 2010 to 2015, there was explosive growth after 2016. Moreover, the citation frequency in 2022 was 2942, 3.77 times that in 2016, indicating that the use of CAT among patients with NP has become a research hotspot and deserves attention.

Figure 2.:

Publications and citations. Annual output and annual citations of publications.

3.2. National and regional contributions

In order to see the contribution of different nations to the field, we analyzed the countries of the documents. We visualized the cooperation between 46 countries on a world map via VOSviewer. In Figure 3A, the countries studying this field are mainly located in Asia, North America, and Europe. China has the most articles and works more closely with the United States. Figure 3B shows the publication statistics for each country in the past 20 years, and the top 5 contributors are China (445, 49.55%), the United States (196, 21.83%), South Korea (107, 11.92%), Japan (43, 4.79%) and the United Kingdom (30, 3.34%). Meanwhile, Table 1 counts the top 10 countries according to the volume of publications and citations per paper. The top 3 countries for the average citation times are Denmark (264.50), Singapore (103.33), and Austria (85.29), indicating the high application value of articles from these countries. Notably, the UK and Italy are not only ranked in the top 10 most published articles, but also in terms of the average citation times. It suggests that the articles from these 2 nations are of high-quality and have a high impact on the field.

Table 1 - Top 10 countries in terms of publication volume and citation per paper. Rank Ranking of publication volume Ranking of citations per paper Country Documents Total citations Citations per paper Country Documents Total citations Citations per paper 1 China 445 6656 14.96 Denmark 2 529 264.50 2 USA 196 6541 33.37 Singapore 3 310 103.33 3 South Korea 107 2035 19.02 Austria 7 597 85.29 4 Japan 43 749 17.41 France 7 592 84.57 5 UK 30 1222 40.73 Sweden 8 656 82 6 Germany 29 652 22.48 Egypt 1 59 59 7 Canada 28 904 32.29 Netherlands 8 401 50.13 8 Italy 24 970 40.42 UK 30 1222 40.73 9 Brazil 17 279 16.41 Italy 24 970 40.42 10 Iran 15 291 19.40 Burkina Faso 1 40 40
Figure 3.:

Countries and Institutions. (A) Geo-visualization map of country cooperation. (B) Statistics on the number of articles published by country from 2002 to 2022. (C) Overlay map of main institutions in co-authorship. The node size represents the number of publications by institutions, the lines between nodes represent the cooperative relationship between institutions, and the color represents the average publication time of articles from this institution.

3.3. Analysis of institutions

In this study, 1102 organizations were counted. Table 2 shows the top 15 organizations in terms of the publication volume, of which 12 are from China. The top 3 organizations were Kyung Hee University (n = 63), Zhejiang Chinese Medical University (n = 42), and China Academy of Chinese Medical Sciences (n = 35). The University of Maryland has only 15 publications, but it has an average citation of 72.2, suggesting that articles from this institution have a greater impact on the field of CAT and NP. Figure 3C shows an overlay map of organizations in co-authorship. In Figure 3C, Kyung Hee University cooperated closely with Seoul National University and Korea Institute of Oriental Medicine, and the Affiliated Hospital of China Medical University cooperated closely with China Academy of Chinese Medical Sciences. However, most of them are domestic institutions collaborating with each other, suggesting the need for increased international institutional cooperation. In addition, Guangzhou University of Chinese Medicine, Nanjing University of Chinese Medicine, Chengdu University of Traditional Chinese Medicine and Clalit Health Services are all in red, indicating that they have paid more interest to this area in recent years.

Table 2 - The top 15 institutions in terms of the number of publications. Rank Institution Country Publications Total citations Citations per paper 1 Kyung Hee University South Korea 63 1360 21.59 2 Zhejiang Chinese Medical University China 42 592 14.10 3 China Academy of Chinese Medical Sciences China 35 488 13.94 4 China Medical University China 32 577 18.03 5 Fudan University China 30 698 23.27 6 Shanghai University of Traditional Chinese Medicine China 29 286 9.86 7 Beijing University of Chinese Medicine China 28 266 9.5 8 Korea Institute of Oriental Medicine South Korea 21 311 14.81 9 China Medical University Hospital China 21 301 14.33 10 Chengdu University of Traditional Chinese Medicine China 18 189 10.50 11 Peking University China 16 767 47.94 12 Guangzhou University of Chinese Medicine China 16 94 5.88 13 Nanjing University of Chinese Medicine China 16 144 9.00 14 University of Maryland USA 15 1083 72.20 15 Wenzhou Medical University China 15 155 10.33
3.4. Analysis of authors and co-cited authors

A total of 4455 authors were included in the data of this study. Table 3 lists the top 20 authors who have published the most papers, with Fang JQ ranking first with 27 articles, followed by Kim SK (17 articles), Liu JL (14 articles), Wang JY (13 articles). At the same time, Lao L 9 articles had a citation count of 637 (70.78 average citation), suggesting that he was influential within the field. Figure 4A is the network visualization of authors, showing the collaboration between authors. The most active in this area was the Fang JQ team, which collaborated closely with other authors.

Table 3 - Top 20 authors and co-cited authors in the number of papers. Rank Author Co-cited author Author Publication Total citations Citations per paper Author Total citations 1 Fang JQ 27 458 16.96 Han JS 238 2 Kim SK 17 372 21.88 Zhang RH 168 3 Liu JL 14 220 15.71 Dworkin RH 113 4 Shao XM 13 221 17 Vickers AJ 100 5 Wang JY 13 212 16.31 Ji RR 97 6 Kim W 13 206 15.85 Zhao ZQ 96 7 Lang Y 12 295 24.58 Zhang Y 94 8 Gao YH 12 193 16.08 Huang C 90 9 Jiang SH 12 173 14.42 Bao T 90 10 Tu WZ 12 173 14.42 Kim JH 87 11 Min BL 11 319 29 Zimmermanm M 85 12 Du J 11 213 19.36 Wang Y 84 13 Chen SP 11 181 16.45 Finnerup NB 83 14 Qiao LN 10 185 18.5 Kim SK 82 15 He XF 10 130 13 Kwon YB 81 16 Ha IH 10 100 10 Burnstock G 79 17 Fang J 9 140 15.56 Bennett GJ 78 18 Lao L 9 637 70.78 Hershman DL 69 19 Wang YQ 9 200 22.22 Lee JH 62 20 Jiang YL 8 115 14.38 Chaplan SR 62
Figure 4.:

Authors and co-cited authors. (A) Network visualization of authors. The node sizes represent the number of publications by the authors, and the connecting lines between the nodes represent the cooperation between the authors. (B) Network visualization co-cited authors. The node size represents the authors’ citation frequency, and the connecting line between the nodes represents the co-citation relationship between the authors.

The top 20 coauthors are shown in Table 3. In the table, the most cited researcher is Han JS with 238 citations, followed by Zhang RH, Dworkin RH, and Vickers AJ with 168, 113, and 100 citations, respectively, which are all more than 100 citations, suggesting that they are highly visible researchers in the field. VOSvierw generated a visualization map of co-cited authors, of which 586 cited authors were cited more than or equal to 10 times, as shown in Figure 4B. As we have seen, Zhang RH and Dworkin RH had a large influence, Vickers AJ had a wider range of influence, however, Han JS had a large and comprehensive influence.

3.5. Journal analysis

In total, 324 journals published 898 publications. The top 10 journals are listed in Table 4, with Evidence-Based Complementary and Alternative Medicine publishing the most content (7.0% of all articles) with 63 articles and 869 citations. The highest average citation per article is the Journal of Pain (24.56 average citations), with 16 articles and 393 citations. However, Q1 and Q2 journals accounted for only 33% of the top 10 journals, suggesting that the field needs more high-quality articles. The network map of journals with no <20 co-citations is shown in Figure 5. The co-citation frequency of journals is represented by node size, with larger nodes indicating a higher co-citation frequency. In this case, Pain had the highest co-citations (n = 2733) and the largest weight.

Table 4 - The top 10 productive journals on CAT for neuropathic pain. Rank Journal Documents Total citations Citations per paper IF (2022) JCR 5-yesr IF 1 Evidence-Based Complementary and Alternative Medicine 63 869 13.79 - Q3 3.014 2 Medicine 50 117 2.34 1.6 Q3 1.9 3 Acupuncture in Medicine 29 463 15.97 2.5 Q3 2.6 4 Journal of Pain Research 27 266 9.85 2.7 Q3 3.2 5 Frontiers in Neuroscience 20 150 7.5 4.3 Q2 5.2 6 Journal of Pain 16 393 24.56 4.0 Q2 5.6 7 Journal of Alternative and Complementary Medicine 13 318 24.46 2.6 Q3 2.8 8 Trials 13 78 6 2.5 Q3 2.5 9 Bmc Complementary and Alternative Medicine 12 249 20.75 - Q1 4.479 10 Molecular Pain 12 207 17.25 3.3 Q3 3.4

CAT = complementary and alternative therapy.

Figure 5.:

Network visualization of journals co-citation. Larger nodes indicate that the journal is cited more frequently.

We show the citation relationships between journals using dual-map overlay mapping. As shown in Figure 6, the citation path between journals is shown by the connecting line between the citing journal on the left and the cited journal on the right. These lines help us familiarize the interdisciplinary relationships in the field. In this study, articles in the area of medicine, medical, clinical are obviously influenced by the areas of molecular, biology, genetics (z = 3.75, f = 1611) and health, nursing, medicine (z = 3.02, f = 1328).

Figure 6.:

Dual-map overlay of journal. Citing journals on the left, cited journals on the right, and connecting lines indicate citation paths between journals. The vertical axis of the ellipse in the figure is positively correlated with the number of journal publications and the horizontal axis is positively correlated with the number of authors.

3.6. Keyword and hotspots

A total of 3461 keywords were counted, of which 360 with a frequency of at least 5 times were used to generate density visualization map using VOSvierw. Figure 7A shows that the research density in this area focuses on “neuropathic pain,” “acupuncture,” “electroacupuncture,” “model,” “pain,” “management” and “inflammatory.” Figure 7B shows the keyword co-occurrence map, consisting of 359 nodes, in which “neuropathic pain” and “acupuncture” have the highest frequency, while “double blind” and “mechanical allodynia” have the highest centrality. Table 5 lists the top 10 keywords in frequency and centrality. The keywords of “acupuncture” (166, 0.17), “peripheral neuropathy” (79, 0.22) and “double blind” (66, 0.31) are ranked in the top 10 in frequency and centrality at the same time, indicating that they are the key nodes of this field and worthy of in-depth study.